title: Reactive oxygen species are required for 5-HT-induced transactivation of neuronal platelet-derived growth factor and TrkB receptors, but not for ERK1/2 activation.
abstract: High concentrations of reactive oxygen species (ROS) induce cellular damage, however at lower concentrations ROS act as intracellular second messengers. In this study, we demonstrate that serotonin (5-HT) transactivates the platelet-derived growth factor (PDGF) type β receptor as well as the TrkB receptor in neuronal cultures and SH-SY5Y cells, and that the transactivation of both receptors is ROS-dependent. Exogenous application of H₂O₂ induced the phosphorylation of these receptors in a dose-dependent fashion, similar to that observed with 5-HT. However the same concentrations of H₂O₂ failed to increase ERK1/2 phosphorylation. Yet, the NADPH oxidase inhibitors diphenyleneiodonium chloride and apocynin blocked both 5-HT-induced PDGFβ receptor phosphorylation and ERK1/2 phosphorylation. The increases in PDGFβ receptor and ERK1/2 phosphorylation were also dependent on protein kinase C activity, likely acting upstream of NADPH oxidase. Additionally, although the ROS scavenger N-acetyl-l-cysteine abrogated 5-HT-induced PDGFβ and TrkB receptor transactivation, it was unable to prevent 5-HT-induced ERK1/2 phosphorylation. Thus, the divergence point for 5-HT-induced receptor tyrosine kinase (RTK) transactivation and ERK1/2 phosphorylation occurs at the level of NADPH oxidase in this system. The ability of 5-HT to induce the production of ROS resulting in transactivation of both PDGFβ and TrkB receptors may suggest that instead of a single GPCR to single RTK pathway, a less selective, more global RTK response to GPCR activation is occurring.
authors.affiliation: Department of Biology, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Kruk
authors.forename: Maryam S
authors.initials: MS
authors.lastname: Vasefi
authors.forename: John J
authors.initials: JJ
authors.lastname: Heikkila
authors.forename: Michael A
authors.initials: MA
authors.lastname: Beazely
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D019255:NADPH Oxidases / Q000378:metabolism; D009474:Neurons / Q000201:enzymology*; D010766:Phosphorylation / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D020813:Receptor, trkB / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*; D015533:Transcriptional Activation / Q000187:drug effects*
chemical_list: D017382:Reactive Oxygen Species; D012701:Serotonin; D019255:NADPH Oxidases; D020797:Receptor, Platelet-Derived Growth Factor beta; D020813:Receptor, trkB; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3